Heterogeneous Soft Materials Research Articles

Results of the literature seem to be consistent with our experience of the soft magnetic composite materials to advance that they magnetize by spin rotations rather than by domain wall motions. We have thus proposed to express the effective magnetic susceptibility as varying with the magnetic fraction through a parameter of microstructural origin (N), and a factor connected to the magnetic character of the substance (X i ). This work shows that X i may be represented by X rot (rotational magnetization), and not by the susceptibility of the bulk matter. Some compositions of ferrites (Ni-ferrites, YIG) for which X rot was known, gave a good confirmation of the above assumption. For other materials, it was necessary to determine X rot experimentally. The technique used is described briefly. It has been sucessfully tested on the ferrites mentioned above. Owing to this calibration, the apparatus is ready now to measure X rot on various dense magnetic matters before they are ground then mixed with resin to be investigated as a function of the magnetic load with the intent to extract the parameter X i . This study is very important for all the applications in which both high susceptibtilities and wide frequency bands are required simultaneously.